Optical device and optical module provided with optical device

Details Optical device and optical module provided with optical device Optical device and optical module provided with optical device

2000-06-21

2002-03-26

Sanghavi, Hemang (Department: 2874)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S039000, C385S049000, C385S052000

Reexamination Certificate

active

06361222

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an optical device, used for, e.g., optical communication or the like, and an optical module provided with the optical device.
Conventionally, an optical device
41
that uses an optical fiber
43
shown in
FIG. 5
or the like, an optical device
51
(shown in
FIG. 6
) described in Jpn. Pat. Appln. KOKAI Publication No. 8-190026, etc. are known as optical transmission-reception devices that are applicable to optical communication, for example.
The optical device
41
shown in
FIG. 5
comprises a substrate
42
, optical fiber
43
, laser diode
44
, photodiode
45
, filter
46
, etc.
The substrate
42
, which is formed of a silicon single crystal, is provided with a V-groove
47
. The optical fiber
43
is located in the V-groove
47
. The laser diode
44
emits signal light beams toward an end face of the optical fiber
43
. The photodiode
45
is located over the optical fiber
43
. The filter
46
is located dividing the optical fiber
43
. The filter
46
guides signal light beams with wavelengths different from the wavelengths of signal light beams that are emitted from the laser diode
44
to the photodiode
45
, among other signal light beams transmitted in the optical fiber
43
.
The optical fiber
43
of the optical device
41
is connected optically to an optical fiber of an external device such as a connector used for optical communication. In other words, the optical device
41
and the external device are connected optically to each other by means of the optical fibers. Thus, the optical device
41
and the external device can be connected relatively easily, and a loss attributable to the connection is relatively small. In attaching the optical fiber
43
to the substrate
42
, moreover, the optical fiber
43
can be positioned with relatively high accuracy with respect to the substrate
42
in a manner such that the optical fiber
43
is fitted in the V-groove
47
. Accordingly, the optical fiber
43
that is attached to the substrate
42
can be also connected optically to an optical waveguide of the external device with relatively high accuracy.
In manufacturing the optical device
41
, the laser diode
44
and the photodiode
45
must be arranged on or soldered to the substrate
42
in a manner such that the optical fiber
43
, which is relatively thin and fragile, is attached to the substrate
42
. In some cases, the optical fiber
43
may be damaged during this operation. If the optical fiber
43
is damaged, the volume of transmission of signal light per unit time is reduced, so that the yield of the optical device
41
itself lowers. Thus, the optical device
41
is liable to cost higher.
On the other hand, the conventional optical device
51
shown in
FIG. 6
is provided with a planar lightwave circuit
52
. A laser diode
53
that functions as a light emitting device, a pair of photodiodes
54
a
and
54
b
that function as light receiving devices, and a filter
55
are arranged in predetermined positions on the planar lightwave circuit
52
.
The planar lightwave circuit
52
is formed on a substrate
56
that is formed of a silicon single crystal. The lightwave circuit
52
is provided with a core
57
and a cladding
58
that have different refractive indexes. The core
57
and the cladding
58
consist mainly of SiO
2
or the like. The paired photodiodes
54
a
and
54
b
are connected optically to the core
57
of the planar lightwave circuit
52
.
The core
57
and the cladding
58
are formed by a film forming method, such as flame hydrolysis deposition (FHD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).
In this optical device
51
, individual waveguides can be formed collectively on the one substrate
56
by the aforesaid film forming method or fine processing technique such as photolithography. Thus, the productivity is high.
In the case of this optical device
51
, however, alignment of the respective optic axes of the core
57
and the optical fiber of the external device requires precise adjustment operation. Since the photodiodes
54
a
and
54
b
are incorporated in the lightwave circuit
52
, moreover, the respective optic axes of the photodiodes
54
a
and
54
b
and the core
57
must be accurately aligned with one another. Thus, assembling the optical device
51
requires more labor and time, so that the cost tends to increase. Furthermore, the necessary time and labor for the optical connection of the optical device
51
to the external device also increase.
Accordingly, the object of the present invention is to provide an optical device, which can be produced with improved yield that permits a reduction in cost and can facilitate connection with an external device, and an optical module provided with the optical device.
BRIEF SUMMARY OF THE INVENTION
The optical device of the present invention comprises a substrate having a flat reference surface and a V-groove recessed from the reference surface, and an optical waveguide formed on the reference surface of the substrate and having a core extending along the reference surface.
In the optical device of this invention, the relative positions of the V-groove and the optical waveguide can be accurately maintained by the CVD or other film forming method or fine processing technique such as photolithography. In this optical device, moreover, the core of the optical waveguide is covered by means of a cladding. In attaching or soldering light emitting and receiving devices, which are attendant to the optical waveguide, to the optical waveguide, therefore, the core can be prevented from being damaged. Accordingly, the yield of production of the optical device can be improved, so that the cost can be lowered.
In the optical device of this invention, moreover, the relative positions of the V-groove and the core can be maintained accurately. By fitting, for example, a locating pin of an external device that has an optical fiber into the V-groove, therefore, the respective optic axes of the core and the optical fiber of the external device can be easily connected with high accuracy. Thus, the labor and time required by the connection between the optical device and the external device can be lessened, so that the optical device and the external device can be connected with ease.
In the optical device of this invention, the optical waveguide may be provided with a filter capable of transmitting a signal light beam with a first wavelength transmitted through the core and reflecting a signal light beam with a second wavelength transmitted through the optical waveguide. Preferably, moreover, the substrate is formed of a silicon single crystal and has the V-groove formed by anisotropic etching. According to this invention, the relative positions of the V-groove and the optical waveguide can be maintained more accurately.
The optical device of this invention may be constructed so that it further comprises a light receiving device located on the optical waveguide and a light emitting device for delivering the signal light beam with the first wavelength to the core of the optical waveguide, and that the filter is located on the optical waveguide so as to divide the core of the optical waveguide between first and second portions, and the filter reflects the signal light beam with the second wavelength toward the light receiving device.
In this case, the light receiving device is located beside the optical fiber, so that a photodiode of the plane reception type can be used as this light receiving device. The photodiode of the plane reception type entails relatively low cost, and besides, has a relatively wide light receiving surface, so that it can ease the positioning accuracy that is required when the optical device is provided with the photodiode. These circumstances are advantageous to reduction in cost.
An optical module of this invention comprises a first optical device and a second optical device. The first optical device includes a substrate having a flat first reference surface and a first V-groove recessed from th

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